The present invention relates to dewatering aqueous-solids by-product streams in alcohol production from grains and plant fibers. More specifically, this invention relates to an improved method for dewatering such stillage to produce solids useful for animal feeds.
In the production of fuel alcohol from plant materials, the biomass is mixed with hot water to produce a wort. The wort is fermented until the final alcohol level is reached. The fermented contents are typically discharged as a slurry to a beer well and to a beer still, which removes the alcohol by distillation. After distillation, the reminder typically includes still bottoms, stillage or whole stillage, and consists mostly of water with spent solids.
The whole stillage has a complex composition. For example, whole stillage from corn fermentation includes non-fermented fibers from the hull and tip cap, particles of the corn germ, oil and other lipids, non-fermented portions including gluten, un-reacted starches, soluble proteins and enzymes, and dead yeast cells. The particle sizes range widely from about 1-2 millimeters to below about 10 microns. Typically, this stillage is dewatered to produce animal feed, which helps offset the waste disposal costs.
What is needed is an apparatus and method for dewatering whole stillage that requires less energy, reduces the amount of suspended solids reaching the evaporator, and recovers beneficial nutrients.